The present invention relates generally to backup of data, and more particularly to reducing a size of backup data in a storage space.
To prevent data loss caused by an error in operation, a software fault, or a hardware fault, it becomes necessary to back up data. The amount of backup data is likely to be enormous. To reduce the amount of backup data, techniques of data compression or data deduplication have been conventionally used. The data compression is a technique to find bit strings having identical contents from target data and to replace the bit strings with short signs. The data deduplication is a technique to find blocks having identical contents from target data and to leave only one of the blocks while deleting the others. These conventional techniques produce an effect if a large number of portions with identical bit strings appear in files; otherwise, these techniques produce less effect. For example, in a case where a result of editing video materials is stored as a video work, and both the video materials and the video work are stored. In the editing operation of simply cutting unnecessary scenes, there are many identical bit strings in both the pre-edited video materials and the post-edited video work; therefore, it can be expected that the conventional techniques effectively work. However, in some cases, special effects are added to many scenes, or the video work is re-encoded for various types of resolution or codecs to be stored so that the video work can be watched by various types of equipment. In these cases, it cannot be expected that many identical bit strings exist in both the pre-edited video materials and the post-edited video work; accordingly, the conventional techniques may produce less effects.